The microbiome of buried soils demonstrates significant shifts in taxonomic structure and a general trend towards mineral horizons.

Burial mounds represent a challenge for microbiologists. Could ancient buried soils preserve microbiomes as they do archaeological artifacts? To investigate this question, we studied the soil microbiome under a burial mound dating from 2500 years ago in Western Kazakhstan. Two soil profile cuts were established: one under the burial mound and another adjacent to the mound surface steppe soil. Both soils represented the same dark chestnut soil type and had the same horizontal stratification (A, B, C horizons) with slight alterations. DNA samples isolated from all horizons were studied with molecular techniques including qPCR and high throughput sequencing of amplicon libraries of the 16S rRNA gene fragment. The taxonomic structure of the microbiome of the buried horizons demonstrated a deep divergence from ones of the surface, comparable to the variation between different soil types (representatives of the soil types were included in the survey). The cause of this divergence could be attributed to diagenetic processes characterized by the reduction of organic matter content and changes in its structure. Corresponding trends in the microbiome structure are obvious from the beta-diversity pattern: the A and B horizons of the buried soils form one cluster with the C horizons of both buried and surface soil. This trend could generally be designated as 'mineralization'. Statistically significant changes between the buried and surface soils microbiomes were detected in the number of phylogenetic clusters, the biology of which is in the line of diagenesis. The trend of 'mineralization' was also supported by PICRUSt2 functional prediction, demonstrating a higher occurrence of the processes of degradation in the buried microbiome. Our results show a profound shift in the buried microbiome relatively the "surface" microbiome, indicating the deep difference between the original and buried microbiomes.

[Description of the phylogenetic structure of hydrolytic prokaryotic complex in the soils].

With the help of the molecular-biological method of cell hybridization in situ (FISH), the abundance of a physiologically active hydrolytic prokaryotic complex in chernozem and gley-podzolic soils is determined. The total proportion of metabolically active cells, which were detected by hybridization with universal probes as representatives of the domains Bacteria and Archaea, in samples of the studied soil, was from 38% for chernozem up to 78% for gley-podzolic soil of the total number of cells. The differences in the structure of chitinolytic and pectinolytic prokaryotic soil complexes are detected. Along with the high abundance of Actinobacteria and Firmicutes in the soils with chitin, an increase in phylogenetic groups such as Alphaproteobacteria and Bacteroidetes is observed.

[Monitoring of the chitinolytic microbial complex of the phylloplane].

A comprehensive study of chitinolytic microbial complexes of the phylloplane from cultured and forest plants has been conducted. An increase of the number and biomass of metabolically active cells of the representatives of the domain Bacteria and a decrease in fungal biomass in the experimental microcosms have been shown to occur after the introduction of chitin. The characteristic features of the taxonomic structure of metabolically active chitinolytic complexes of the phylloplane of the plants studied have been elucidated. Representatives of the phyla Proteobacteria, Bacteroidetes, and Verrucomicrobia have been shown to play important roles in the chitinolytic complexes of green leaf samples, while mycelial actinobacteria of the phylum Actinobacyteria played a similar role in needles of coniferous trees. A collection of chitinolytic microorganism cultures isolated from the phylloplane of different plant species has been created.